Update CMakeLists.txt to require CMake version 3.13 and set policy for compatibility

CMakeLists.txt

@@ -185,6 +185,9 @@ endif()
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
 # Add slog submodule
+if(POLICY CMP0000)
+  cmake_policy(VERSION 3.5)
+endif()
 add_subdirectory(3rdparty/slog)
 
 include_directories(include 3rdparty/uthash/src)

tests/CMakeLists.txt

@@ -1,3 +1,5 @@
+cmake_minimum_required(VERSION 3.13)
+
 # 'Google_test' is the subproject name
 project(tests)